A number of hydroxylated derivatives of cholocalciferol have been isolated as metabolites of cholecalciferol, and these have been found to be more potent than the parent compound, vitamin D.sub.3. Thus, 25-hydroxy-21,25-dihydroxy- and 1,25-dihydroxy-cholecalciferol exhibit distinctive physiological activity and are of substantial importance in medicine.
According to the present invention there is provided a novel and simple process for the preparation of hydroxylated derivatives of cholesterol and of 7-dehydroxycholesterol, which are intermediates in the preparation of these and of other hydroxylated derivatives of cholecalciferol.